Solar energy spreads in broad wavelengths from infrared to the ultraviolet (UV) spectra. Solar energy can be absorbed for the generation of electricity through the use of semiconductor materials on a solar panel. In the process of generating electricity, the bandgap energy of the p-n junction of the semiconductor materials determines the range of wavelength of the solar energy that can be absorbed by semiconductor materials applied on the solar panel. Solar energy outside the bandgap energy of the solar panel can not be absorbed for electricity generation. Due to the limitation on the bandgap energy of the p-n junction of the commonly used semiconductor materials, most solar panels absorb solar energy only in a limited wavelength, such as visible light.
In addition, most commonly used solar panels are flat solar panels or two-dimensional solar panels that allow sunlight to interact with the solar cell only once. Hence, the majority of the sunlight is reflected rather than being absorbed. This causes low efficiency of the commercial solar panels on sunny days, and even lower efficiency on cloudy and rainy days.